Spontaneously inflammable flashlight composition and method of preparation



Patented Mar. 7, 1939 UNITED STATES SPONTANEOUSLY PATEN'l orrlcs FLASH- LIGHT COMPOSITION AND DIETHOD OF PREPARATI N Richard E. Voiirath, Angeles, 0alif.

No Drawing. Application August :9, 1937, Serial No. 158,115

1': Claims. 01. 5 2-24)- My invention relates to the pyrotechnic art and particularly to spontaneously-acting chemical means for producing a flash of light. My invention has an important application in photography through the possibility of providing an intensely bright light of very short duration.

An object of my invention is to provide a spontaneously inflammable composition.

Another. object is to provide a spontaneously inflammable composition which is capable of emitting an intense flash of light suitable for photographic purposes.

Another object of the invention is to provide a composition which is spontaneously inflammable in gas containing oxygen.

A further object is to provide a spontaneously combustible composition whichis very rapid in its combustion.

Still another. object of my invention is to provide methods of making my spontaneously inflammable flash light composition.

At the present time there are in common .use two methods of producing an instantaneous flash of light for photographic purposes. One of these methods involves the combustion of flashlight powders which, in general, consist of a-mixture of a combustible metallic powder, such as magnesium, and a powdered oxidizing agent such as barium peroxide. The other method involves the combustion of aluminum foil in a glass bulb containing oxygen. In both cases, combustion is usually started by electrically heating a suitable fuse wire in contact with the combustible material. The results obtained by the use 01' aluminum foil and gaseous oxygen are superior to those obtained by the use'of flash light powders because the foil burns with greater rapidity and'brilliance,

and because during the combustion of a flash light powder of the type commonly used, the oxidizing agent, after having been reduced, ispr'es ent' as a solid which absorbs a considerable amount of the heat of the combustion and also covers up the particles of burning aluminum, both of which eflects reduce the intensity of the light emitted. I

The ideal method for producing a flash of light 'is to burn aluminum, magnesium, or other suit;

able combustible metallic powder in oxygen. Finely divided aluminum, for example, when once ignited, burns withgreat rapidity owing to the relatively large surface exposedby a powder. It is, however, extremely diflicult to ignite such a powder because lack of coherence between the particles of powder prevents combustion from spreading from one particle'to the next. To form the powder into a relatively compact mass would not avoid the-difficulty, for this would defeat the purpose of using a powder, namely, to promote rapid combustion. If such a compact mass .of powder is ignited in oxygen, the combustion proceeds rather slowly and a flare results instead of a flash. v

I have solved the problem of igniting a rapidly combustible powder by mixing with it a pyrophoric substance. I employ the term pyrophoric to" describe any substance which ignites and burns spontaneously in a suitable gas without requiring deliberate application of heat to start combustion. An example of a pyrophoric substance is pyrophoric iron which ignites spontaneously in oxygen. A yrophoric form of iron has been for over one hundred years; but while it is known how to produce the pyrophoric iron, much confusion still exists regarding the theory of its action. Extreme fineness of division appears essential but does not entirely explain its properties. Another example of a pyrophoric substance is yellow phosphorus which burns spontaneously in chlorine. Compounds may also constitute pyrophoric substances, as for example, the liquid alureco'gnized and well-known in the chemical art minum trimethyl which is spontaneously inflamsubstance, and to form a mixture of these substances. Such a composition has the property of 3 and rapidly burning with emission light, which property is not possessed by ex of the components of the composition separate Pyrophoric iron ignites spontaneouslyin'} oxyg and becomes red hot but emits no useful amount" spontaneously igniting in the presence of oxygen-Q of an'inten'se:

of light, while aluminum powder alone will notignite spontaneously in oxygen. But in a mixture,

these substances cooperate so that when the mixture is exposed to oxygen, combustion of both- 'ingredients immediately takes place and a brilliant flash of light highly suited for photographic purposes is produced. The eil'ectiveness of my compositions is largely due to the fact that particles of pyrophoric substance adhere to each of the particles of combustible powder, and in this way each particle of combustible powder is equipped with its own igniter. When the above described composition is exposed to oxygen, each rticle of pyrophoric iron rapidly oxidizes and 2 heat generated thereby raises the temperature the adjoining aluminum particle to the point iere it will ignite, and in this manner the ene mass ignites and burns practically instantaously.

The method which I have found most effective producing a composition of the type described ove consists in mixing approximately equal rts of finely powdered ferrous oxalate and powred aluminum, and thereafter heating the mixre to a temperature of about 4'75 C. for a time fidcient to decompose the ferrous oxalate. Durg this heating the ferrous oxalate decomposes ainly in accordance with the following reaction:

he iron produced by this reaction is pyrophoric id ignites spontaneously in air or in oxygen,

ie particles of iron becoming red hot as soon they come into pontact with air or oxygen. he mixture of pyrophoric iron and aluminum repared in this manner ignites instantly upon sing scattered in oxygen and burns with great ipidity emitting a brilliant flash of light which tsts for less than one hundredth of a second 'hen about 50 milligrams of aluminum are used 1 the mixture burned.

It is convenient to prepare the spontaneously riflammable composition for use in photography y placing a suitable quantity of the mixture of errous oxalate and aluminum powder in a small asily-breakable glass bulb of about 1 cubic centineter volume having a stem attached through which the bulb is open to the atmosphere. The )lllb and its contents are then heated in a furnace it a temperature of about 475 C. for severalninutes, after which the stem of the bulb is sealed MI by fusion of the glass. The time required to form the spontaneously inflammable composition iepends to some degree on the bulb employed and ;he quantity of the mixture being prepared, but the required time and temperature may readily be determined for any desired quantity by simple tests in which the spontaneous infiammability of the resulting composition in oxygen is the criterion of success. I have found that for quantities of mixture containing less than one tenth of a gram of aluminum in a .bulb as described, a heating time of 5 minutes is suflicientat a temperature of about 475 C. If it is desired to prepare a larger amount of the composition, the heating may be carried out in a glass or other suitable vessel provided with a gas delivery tube.

The completion of the process may be determined" by noting when the evolution of carbon dioxide has substantially ceased. The mixture may then be stored by sealing the vessel or by maintaining it in an enclosure filled with carbon dioxide, nitrogen, or some other inert gas.

An alternative method of preparing my spontaneously inflammable composition comprises mixing iron oxide and powdered aluminum and acting upon the mixture with a reducing gas such as hydrogen at a temperature of about 500 C. for about one hour. The hydrogen reduces the iron oxide to pyrophoric iron and the resulting mixture of this with the aluminum powder spontaneously burns with greater vigor upon exposure to oxygen. A great many varieties of iron oxide prepared by many difierent methods are obtainable onthe market. A variety which I have found particularly suitable is one known as optical rouge used for polishing lenses in optical work. Another suitable variety of iron oxide is siderable time is to elapse that prepared by precipitation from an aqueous solution of ferric nitrate with ammonia water followed by washing and drying. In all cases the iron oxide should be very finely ground so as to be an impalpable powder. In preparing the spon-. taneously inflammable composition, by this method, for use in photography, it is convenient to place the desired amount of iron oxide and aluminum powder in approximately equal quantitles in small glass bulbs of the type previously described. A number of such bulbs are placed in a reducing furnace kept at about 500 C. and through which a slow stream of hydrogen, or other reducing gas, is passed. After the reduction process is complete, .as may be determined by preliminary trial runs, the stems of the bulbs are sealed off by fusion of the glass. If a conbetween removing the bulbs from the furnace and sealing them, it is best to keep them in a container filled with an inert gas such as nitrogen or carbon dioxide; otherwise oxygen from the air enters the bulbs and oxidizes the pyrophoric iron, rendering it inactive for the present purpose.

In my spontaneously inflammable flash light compositions, I may employ for the combustible powder, in place of aluminum, magnesium powder, zinc powder, powdered red phosphorous, lanthanum, or equivalent substances. The requirement of this constituent is that it shall, when once ignited, be rapidly combustible with emission of light. Materials of this type are spoken of as flash materials. The same procedure may be followed in making the composition with any of these combustible substances as has been described using aluminum.

With any of these flash materials, I may alternatively employ in my composition as the pyrophoric substance, in place of pyrophoric iron, pyrophoric lead. Pyrophoric lead may be prepared by heating lead tartrate at about 475 C. During the decomposition a smoke escapes as long as there is any undecomposed lead tartrate left and since the smoke has an odor similar to that of burnt sugar, it is a simple matter to estimate the completion of the process by observing when this odor ceases to be emitted.

I may also form my composition using, as the pyrophoric substance, aluminum trimethyl. In preparing the composition comprising aluminum powder and aluminum trimethyl, I seal up within a glass bulb a mixture of aluminum powder and mercury dimethyl, and heat the mixture for about 24 hours at a temperature of about 100 C. A suitable proportion is 5 parts of aluminum powder to 1 part of mercury dimethyl by weight. During the heating period the mercury dimethyl reacts with the aluminum in accordance with the following reaction:

The liquid aluminum trimethyl thus formed is spontaneously inflammable in oxygen and by its combustion ignites the aluminum powder with which it is mixed. Mercury diethyl may be used in place of mercury dimethyl, but in this case the heating must be carried out for a longer period of time, for example, 48 hours at about 135 C. Also mercury diphenyl may alternatively be used, resulting in the formation of spontaneously inflammable aluminum triphenyl. Since magnesium reacts rather slowly with mercury dimethyl and,

similar compounds, it is desirable, when employing magnesium as the combustible substance in the composition, to use a mixture of powdered magnesium and about one tenth oi its weight of aluminum together with sufllcient mercury dimethyl to convert all of this aluminum into aluminum trimethyl.- In this manner a mixture of magnesium powder and pyrophoric aluminum trimethyl is formed, and when this mixture is exposed to oxygen, the combustion of the spontaneously inflammable aluminum alkyl initiates the combustion of the magnesium.

In producing a brilliant flash of light by means of my spontaneously inflammable flash light compositions above described it is suiflcient to quickly expose them to a gas in which both the flash component and the pyrophoric component of the composition are combustible and in which thepyrophoric component is spontaneously combustible. With respect to the compositions described herein,

oxygen is the preferred gas to which the compositions are exposed. Nitrogen dioxide may also be used, and naturally these combining gases need not be present alone but may be associated in suflicient quantity with other gases. I have described my compositions as preferably being enclosed in small thin glass bulbs; and to produce a flash of light it is then simply necessary to shatter one of these bulbs in an atmosphere of a suitable gas. Methods and apparatus for useof my compositions, including construction and use of the containing bulbs herein mentioned are further described in my concurrently filed application.

It is understood that the compositions and methods of their preparation herein described are given by way of illustration and not by way of limitation. Additional constituents may be added to my compositions for various purposes without departing from the spirit of my invention; and it is recognized that other equivalent compositions and other. methods of preparing the same may suggest themselves to chemists and others skilled in the art.

What I claim is:

1. A spontaneously inflammable composition including a mixture of a substance combustible in a gas, said substance emitting upon combustion substantial quantities of light, and a second substance pyrophoric in said gas.

2. A spontaneously inflammable flash .light composition including a mixture of a flash material and a pyrophoric substance, said pyrophoric substance being pyrophoric in the same gas in which said flash material is combustible.

3. A spontaneously inflammable flash light composition including a mixture 01' a finely divided metal combustible in a gas, said metal emitting upon combustion substantial quantities of light, and a substance'pyrophoric in said gas.

4. A spontaneously inflammable flash light composition including a mixture of a flash material combustible in oxygen, and pyrophoric iron. 5. A spontaneously inflammable flash light compositior. including a mixture of a finely divided metallic substance combustible in oxygen, said substance emitting upon combustion substantial quantities of light, and pyrophoric iron,

6. A spontaneously inflammable flash light composition including a mixture of aluminum powder and pyrophoric iron.

7. A spontaneously inflammable flash light composition including a mixture of a flash material combustible in oxygen, and pyrophoric lead. I 8. A spontaneously inflammable, flash light composition including a mixture of a finely divided metallic substance combustible in oxygen, said substance emitting upon combustion substantial quantities of light, and pyrophoric lead.

9. A spontaneously inflammable flash light composition including a mixture of a.flash material combustible in oxygen, and a spontaneously inflammable aluminum alkyl.

10. A spontaneously inflammable flash light composition including a mixture of a finely divided metallic substance combustible in oxygen, said substance emitting upon combustion substantial quantities of light, and a spontaneously inflammable aluminum alkyl.

11. A method for producing a spontaneously inflammable flash light composition which includes forming a mixture of. a finely divided flash material combustible in oxygen, and ferrous 0xalate, and heating said mixture in the absence of oxygen at a temperature sufliciently high and for a sufiicient time period to decompose the ferrous oxalate to pyrophoric iron. v

12. A method for producing a spontaneously inflammable flash light composition which includes forming a mixture of aluminum powder and ferrous oxalate, and heating said mixture in the absence of oxygen at a temperature sufliciently high and for a suflicient time period to decompose the ferrous oxalate to pyrophoric iron.

13. A method for producing a spontaneously inflammable flash light composition which includes forming a mixture of a finely divided flash material combustible in oxygen and pulverulent iron oxide, and subjecting said mixture to a reducing gas at an elevated temperature for a time period suiflcient to reduce the iron oxide to pyrophoric iron.

14. A spontaneously inflammable flash light composition including a mixture ofa finely divided combustible metal, said metal emitting upon combustion substantial quantities of light, and a pyrophoric substance.

15. A spontaneously inflammable flash light composition including a mixture of a finely divided flash material which is rapidly combustible in a gas, and a' substance pyrophoric in said gas.

16. A method for producing a spontaneously inflammable flash light composition which includes forming a mixture of a finely divided flash material combustible in a gas and a compound of a metal, said metal being capable of a form pyrophoric in said gas, and heating said mixture in the absence of said gas at a temperature sufliciently high and for a suiflcient time period to decompose said compound to produce said metal in the mixture in pyrophoric form.

17. A method for producing a spontaneously inflammable flash light composition which includes forming a mixture of a finely divided flash material combustible in oxygen and lead tartrate,

.and heating said mixture in the absence of oxy- RICHARD H. VOH-RA'I'E. 

